/*
 * Copyright © 2014 Intel Corporation
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 *
 */

#include "i915_drv.h"
#include "i915_gem_batch_pool.h"

/**
 * DOC: batch pool
 *
 * In order to submit batch buffers as 'secure', the software command parser
 * must ensure that a batch buffer cannot be modified after parsing. It does
 * this by copying the user provided batch buffer contents to a kernel owned
 * buffer from which the hardware will actually execute, and by carefully
 * managing the address space bindings for such buffers.
 *
 * The batch pool framework provides a mechanism for the driver to manage a
 * set of scratch buffers to use for this purpose. The framework can be
 * extended to support other uses cases should they arise.
 */

/**
 * i915_gem_batch_pool_init() - initialize a batch buffer pool
 * @engine: the associated request submission engine
 * @pool: the batch buffer pool
 */
void i915_gem_batch_pool_init(struct intel_engine_cs *engine,
                              struct i915_gem_batch_pool *pool)
{
        int n;

        pool->engine = engine;

        for (n = 0; n < ARRAY_SIZE(pool->cache_list); n++)
                INIT_LIST_HEAD(&pool->cache_list[n]);
}

/**
 * i915_gem_batch_pool_fini() - clean up a batch buffer pool
 * @pool: the pool to clean up
 *
 * Note: Callers must hold the struct_mutex.
 */
void i915_gem_batch_pool_fini(struct i915_gem_batch_pool *pool)
{
        int n;

        lockdep_assert_held(&pool->engine->i915->drm.struct_mutex);

        for (n = 0; n < ARRAY_SIZE(pool->cache_list); n++) {
                struct drm_i915_gem_object *obj, *next;

                list_for_each_entry_safe(obj, next,
                                         &pool->cache_list[n],
                                         batch_pool_link)
                        __i915_gem_object_release_unless_active(obj);

                INIT_LIST_HEAD(&pool->cache_list[n]);
        }
}

/**
 * i915_gem_batch_pool_get() - allocate a buffer from the pool
 * @pool: the batch buffer pool
 * @size: the minimum desired size of the returned buffer
 *
 * Returns an inactive buffer from @pool with at least @size bytes,
 * with the pages pinned. The caller must i915_gem_object_unpin_pages()
 * on the returned object.
 *
 * Note: Callers must hold the struct_mutex
 *
 * Return: the buffer object or an error pointer
 */
struct drm_i915_gem_object *
i915_gem_batch_pool_get(struct i915_gem_batch_pool *pool,
                        size_t size)
{
        struct drm_i915_gem_object *obj;
        struct list_head *list;
        int n, ret;

        lockdep_assert_held(&pool->engine->i915->drm.struct_mutex);

        /* Compute a power-of-two bucket, but throw everything greater than
         * 16KiB into the same bucket: i.e. the the buckets hold objects of
         * (1 page, 2 pages, 4 pages, 8+ pages).
         */
        n = fls(size >> PAGE_SHIFT) - 1;
        if (n >= ARRAY_SIZE(pool->cache_list))
                n = ARRAY_SIZE(pool->cache_list) - 1;
        list = &pool->cache_list[n];

        list_for_each_entry(obj, list, batch_pool_link) {
                /* The batches are strictly LRU ordered */
                if (i915_gem_object_is_active(obj)) {
                        struct reservation_object *resv = obj->resv;

                        if (!reservation_object_test_signaled_rcu(resv, true))
                                break;

                        i915_gem_retire_requests(pool->engine->i915);
                        GEM_BUG_ON(i915_gem_object_is_active(obj));

                        /*
                         * The object is now idle, clear the array of shared
                         * fences before we add a new request. Although, we
                         * remain on the same engine, we may be on a different
                         * timeline and so may continually grow the array,
                         * trapping a reference to all the old fences, rather
                         * than replace the existing fence.
                         */
                        if (rcu_access_pointer(resv->fence)) {
                                reservation_object_lock(resv, NULL);
                                reservation_object_add_excl_fence(resv, NULL);
                                reservation_object_unlock(resv);
                        }
                }

                GEM_BUG_ON(!reservation_object_test_signaled_rcu(obj->resv,
                                                                 true));

                if (obj->base.size >= size)
                        goto found;
        }

        obj = i915_gem_object_create_internal(pool->engine->i915, size);
        if (IS_ERR(obj))
                return obj;

found:
        ret = i915_gem_object_pin_pages(obj);
        if (ret)
                return ERR_PTR(ret);

        list_move_tail(&obj->batch_pool_link, list);
        return obj;
}